The publication entitled "Harnisch & Kieth, plaster model location grinder G-F 316" discloses a work-bench of this kind in the form of a grinding machine for cutting locating notches into the bottom of models. The model is moved manually on a Teflon support in a guide against a cemented carbide formed milling cutter, so that the locating notches are milled precisely to shape. The resulting dust is sucked off by built-in exhaust means and deposited in a dust bag. The milling cutter is covered by a movable shield.
In this arrangement the design of the model support, the exhaust means and the safety device is still rather complicated. In particular it is difficult to change the cutter, since the milling table can only be removed with great difficulty and with a special tool. This requires a considerable expenditure of time and effort.
It is also known from British specification 14 62 177, in the case of a high-speed mixer having a shaft that is driven by a hydraulic motor, carries mixing blades and can be raised and lowered so that in the lowered position it extends into a container for the material to be mixed, to take precautions to prevent injury when the shaft is raised. These precautions comprise means for switching off the drive when the shaft is raised and a basket that is fixed around the shaft and extends as far as the mixer blades.